@mamamusic If possible, get yourself to a nephrologist, who specializes in kidneys and their function. Perhaps your internist has a referral name for you!

Finding out the root cause of lowering eGFR is crucial. The two main causes are uncontrolled/untreated diabetes or high blood pressure. Other causes can be long term side effects of certain medications, hereditary factors, and lifestyle. It's worth investigating!
Ginger